SU1488281A1 - Method of producing electric insulating material based of molten magnesium oxide - Google Patents

Description

The invention relates to refractory industry, mainly to the production of materials based on fused magnesium oxide, used for the manufacture of tubular heaters and refractory products. The purpose of the invention is to increase the electrical characteristics by reducing the iron content and increase the homogeneity of the chemical and phase

The invention relates to refractory industry, mainly to the production of materials based on fused magnesium oxide, used for the manufacture of tubular heaters and refractory products.

The aim of the invention is to increase the electrical characteristics by reducing the iron content and increasing the homogeneity of the chemical and phase composition of the material.

The proposed method allows to obtain an insulating material with high electrical characteristics due to the fact that as a result of heat treatment in an oxidizing atmosphere at 900—

composition of the material. After melting the raw material, cooling the block and removing the debris, 50-98% underpayment (agglomerated and partially melted raw material) is removed — the part that does not form a solid monolithic material with the main part of the block. Then the main part of the block containing 75–99% MgO, 0.9–23% oxides of calcium, silicon, aluminum, etc., and 0.06–2.5% of iron impurities in the form of metallic inclusions, oxides of popes; solutions, consisting of the remaining NSA ·,) of the melt and fused magnesium oxide, depending on the purpose, are crushed by pas in; ·: –– o exhaust crushers to a particle size of less than 1 mm; 120047 for 4 h, cooled at a rate of 5 - 5O (a47.4, after which, using an electrically separator, particles of the material containing glands are removed ;, 0.1-2.5% by electromagnetic separation at a magnetic field of a magnetic field 10 ^{e -} 2.10 ^-1 3. The iron content is 0.04- '2.0%. 1 tab.

1200 ° C cooling is carried out with a speed of 5-500 ° C, the phase composition of the material changes, its transformation occurs; in her,. As a result, the magnetic reproducibility of the material increases, and when a magnetic field of 10 * - 2 · 10 'E is applied, it becomes possible to additionally parse iron-containing particles of periclase.

The method is as follows.

After melting raw materials, cooling the block

and scree removal removes 50 -98% of the pedofloop (sintered and partially melted

raw material) - the part that ns forms

durable solid material from the base1488281

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Noah part of the block. Then the main part of the block containing 75--99% MgO, 0.9-23% oxides of calcium, silicon, aluminum, etc., and 0.06-2.5% of iron impurities in the form of metallic inclusions, oxides or solutions (Reo M ^ O; RegOz in M ^ O), consisting of the remaining non-melt and fused magnesium oxide, depending on the purpose, is ground on roller crushers to a particle size less than 1 mm, electromagnetic separation is carried out, and then heat treated in an electric resistance furnace of the SNOL type in the atmosphere air at 900–1200 ° C for 4 h, cooled at a speed of 5–500 ° C / h, speed about cooling is controlled by changing the power of the electric furnace, after which particles of a material with an iron content of 0.1–2.5 wt. are removed using an electromagnetic separator type 138Т. ^and / o electromagnetic separation at a magnetic field strength of 10 2 -10 ¹ E.

Data on the effects of heat treatment temperature, cooling rate and magnitude of the magnetic field on the electrical characteristics of periclase with an average iron content of 0.58% (minimum 0.06%, maximum 2.5%) are presented in the table.

Magnesite is melted on a block in an electric arc furnace, after cooling the block, scree is removed. Then the block is broken and 80% of the subflood is removed. The remaining material is crushed to a particle size of less than 0.6 mm and carry out electromagnetic separation. A powder of the following chemical composition is obtained,%: MgO 96.50; S1O2 0.85; CaO 1.53; HOS = 0.54; Regoz 0.58. Moreover, according to the data of chemical and petrographic analysis, particles with an iron content of 0.06–2.5 wt.% Are found in this powder.

Example 1. The initial powder is thermoablative in an atmosphere of air at 1050 ° C, cooled at a rate of 300 ° C / h and subjected to electromagnetic separation with a magnetic field strength of 2 · 10 ⁴ E. As a result, the material was obtained (60% by weight of the entire material), containing an average of 0.25% RegOz, in the intermediate material to be removed (40% by weight), 1.4% RegOz. In the obtained material according to the chemical analysis, there are particles with an iron content of 0.04–1.6 wt.%, This narrowing of the iron content interval indicates an increase in the homogeneity of the chemical composition of the material.

The scope of the intermediate material is the manufacture of induction furnace linings. The specific breakdown voltage of the material obtained by the proposed method will be 1.9 kV / mm, and by the known method - 0.75 kV / mm.

In examples 2-9 (table), operations according to the modes of the proposed method are carried out in a similar way.

Example 10. The source material is thermally treated at 1300 ° C, cooled at a rate of 300 ° C / h, separated with a magnetic field strength of 2 · 10 ⁴ E. The result is a material (84% by weight) with a content of 0.32% RegOz and an intermediate material (16% by weight) with a content of 1.2% RegOz. The specific breakdown voltage of the material obtained by the proposed and known methods, respectively 1.1 and 0.8 kV / mm.

Going beyond the temperature range of the proposed method towards higher temperatures leads to an increase in the content of RyogOz in the material by 0.03– 0.07% and, accordingly, a decrease in the specific breakdown voltage by 0.5–0.8 kV / mm.

Example II The source material is treated at 800 ° C (below the stated temperature), cooled at a rate of 300 ° C / h, separated with a strength of 2X ⁴ E. The result is a material (87% by weight) with a content of 0.35% RegOz and an intermediate material (13% by weight) with a content of 1.1% RegOz. The specific breakdown voltage of the material according to the proposed and known methods is 1.1 and 0.78 kV / mm, respectively.

Moving beyond the temperature range of the proposed method towards lower temperatures leads to an increase in the content of RegOz in the material by 0.06–0.1% and a decrease in the specific breakdown voltage by 0.6–0.9 kV / mm.

Example 12. The source material is thermally processed at 900 ° C, cooled at a rate of 600 ° C / h, separated with a magnetic field strength of 2 · 10 ⁴ E. As a result, the resulting material (87% by weight) with a content of 0.39% RegOz and intermediate material (13% by weight) with a content of 1.2% RegOz. The specific breakdown voltage of the material according to the proposed and known methods is 1.0 and 0.81 kV / mm, respectively. An increase in the rate of cooling of the material leads to an increase in the content of RegOz in the material by 0.1–0.14%, as well as to a deterioration of the electrical insulating properties, to a decrease in the specific volumetric voltage ng 0.6–0.9 kV / mm.

Example 13. The starting material is thermally treated at 900 ° C, cooled at a rate of 2 ° C / h, separated from magnetic field strengths of 210 ¹ E. The result is a material (75% by weight) with a content of 1.3% RegOz-Specific breakdown voltage of the material according to the proposed and known methods, respectively, 1.7 and 0.82 kV / mm.

Cooling at such a speed results in a material with the same properties as when the specified speed range is observed, but this method is economically unprofitable, as the time spent on the process increases.

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Example 14. The starting material is thermally treated at 1200 ° C, cooled at a rate of 300 ° C / h, separated with a magnetic field strength of 3-10 ⁴ E. The result is a material (37% by weight) with a content of 0.26% RegO3 and an intermediate material (63% by weight) with a content of 1.3% RegOz. The specific breakdown voltage of the material according to the proposed and known methods, respectively, 1.8. and 0.6 kV / mm.

An increase in the magnetic field strength results in the proposed material, however, the amount of intermediate material in which the material also enters, where the iron is within acceptable limits, increases.

Example 15. The source material is thermoablative. at 1200 ° C, cooled at a rate of 300 ° C / h, separated with a magnetic field strength of 2 · 10 ² E. As a result, a material (91% by mass) with a content of 0.39% RegOz and an intermediate material (9% by mass ) with the content of 1.7% RegOz. The specific breakdown voltage of the material according to the proposed and known methods is 0.8 and 0.38 kV / mm, respectively.

A decrease in the magnetic field strength leads to a sharp increase in the content of RegOz in periclase and a decrease in the specific breakdown voltage, since the magnetic field strength of less than 10 ³ Oe is insufficient to remove a portion of the material with a high iron content.

In addition, experimental work was carried out with a purer non-classed powder with an average iron content of 0.08%, there were particles in this powder

with an iron content of 0.06 --- 0.31%. This powder is heat treated in an atmosphere of air at 1050 ° C, cooled at a rate of 500 ° C, / h and subjected to electromagnetic separation with a magnetic field strength of 1-10 'E. As a result, a material (88% by mass) of all the material containing average 0.04% RegOz, in the intermediate product (12% by weight) 0.46% RegOz.

The specific breakdown voltage of the material obtained by the proposed and known methods, respectively 2.4 and 1.7 kV / mm.

The proposed method makes it possible to obtain a very pure chemical composition of the powder of electrochemical periclase with high electrical insulating characteristics.

Claims (2)

Claim (a method for producing an insulating material based on fused magnesium oxide, including melting a magnesium-containing raw material into a block in an electric furnace, subsequent cooling of the block, removal of debris and sub melting, grinding, electromagnetic separation, heat treatment and cooling of the crushed material, characterized in that, in order to improve electrical characteristics by reducing the iron content and increasing the homogeneity of the chemical and phase composition of the material, the heat treatment of the crushed material is carried out at 900-- ¹²⁰⁰ ° C, cooled at a speed of 5 ..... 300 ° C / h, after which additionally carry out electromagnetic separation with a magnetic field strength! 0 ³ —2-10 ¹ E. 7 1488281 eight Well oh. But about with about about 5 X ω С, <5 О С νθ Ж О а ааз and 1G) G- “- GO SP g-SO’— <P SO r ^ slsooosooosog ^ oooog ^ osochat about about about about about about. ooooooooo TSPCHOOKOO ^ SO'OOOOCH’— —- About G * yes with one " about <and N CO 1L G * · KG1 5— ΓΟκΤιΛίΠ- ^ ιΛιΛ ^ ιΛςΤίΛι / Ί'-Λ ι / Ί "- * ~ * - <Τ <ΤΓ * <Γ <3 · (Νθ4τ- <3 · τ-σ \ oοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοο ΟΟΟΟΟΟΟΟΟΟΟΟΟΟ ' ^ οωσ'σ’ίΛΦο ^ ίΛΝΓΟΝ '^' ίΐΛ - ’-’-t-’-’-s ’-’-gchchsch ’-’-c oοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοοο O. Well Well SM ίΝ Γ "4 <4 ΟΟΟΟιηΟκΊΟΟΟΟΟίΜΟΟ Ο Ο Ο ο ο οοοοοοοοο СП сП СО со ιΛ ιη η η т φ <**) SP oh i F 2 O. Eοοοοοοοοοοοοοοο ιηιηΟΟιηιΛΟΟυ’ΊΟΟΟΟΟΟ oosimos'myiulspmsch Mr-N Ο ") Ί ιιΊ 43 I • SOOO'– TANTS <Г1П